Preliminary cost model for space telescopes
Author(s):
H. Philip Stahl;
Frank A. Prince;
Christian Smart;
Kyle Stephens;
Todd Henrichs
Show Abstract
Parametric cost models are routinely used to plan missions, compare concepts and justify technology investments.
However, great care is required. Some space telescope cost models, such as those based only on mass, lack sufficient
detail to support such analysis and may lead to inaccurate conclusions. Similarly, using ground based telescope models
which include the dome cost will also lead to inaccurate conclusions. This paper reviews current and historical models.
Then, based on data from 22 different NASA space telescopes, this paper tests those models and presents preliminary
analysis of single- and multi-variable space telescope cost models.
Observatory conceptual development for the Joint Dark Energy Mission
Author(s):
Michael J. Sholl;
Gary M. Bernstein;
David A. Content;
Michael G. Dittman;
Joseph M. Howard;
Michael L. Lampton;
John P. Lehan;
J. Eric Mentzell;
Robert A. Woodruff
Show Abstract
The Joint Dark Energy Mission (JDEM)1,2 is a proposed dark energy space mission that will measure the
expansion history of the universe and the growth of its large scale structure. It is intended to provide tight
constraints on the equation of state of the universe and test the validity of general relativity. Three
complementary observational analyses will be employed: Baryon Acoustic Oscillations, Type 1a Supernovae
and Gravitational Weak Lensing. An observatory designed for efficient accommodation of these techniques
combines wide-field, diffraction-limited observations, ultra-stable point spread function, and spectroscopy.
In this paper we discuss optical configurations capable of simultaneous wide-field imaging and spectroscopy,
using either afocal or focal telescope configurations. Spectroscopy may be performed by an integral field unit
(IFU), grism or prism spectrometer. We present a flowdown of weak lensing image stability requirements
(the most demanding technique optically) to telescope thermo-mechanical stability limits, based on variations
in the optical transfer function of combinations of Zernike modes, and the sensitivity of these mode
combinations to thermo-mechanical drift of the telescope. We apply our formalism to a representative threemirror
anastigmat telescope and find quantitative relations between the second moments of the image and the
required stability of the telescope over a typical weak lensing observation.
Euclid Mission: assessment study
Author(s):
David Lumb;
Ludovic Duvet;
Renee Laurijs;
Maurice Te Plate;
Isabel Escudero Sanz;
Gonzalo Saavedra Criado
Show Abstract
The Euclid mission has been proposed as a powerful probe of Dark Matter and Dark Energy, using complementary
space-borne imaging and spectroscopy techniques. The mission concept is being assessed as part of the European Space
Agency (ESA) Cosmic Visions 2015-25 programme. The mission concept is described, including some of the critical
trade-offs. The scientific performance predictions are briefly presented.
Assessment study of the SPICA telescope assembly
Author(s):
N. Rando;
O. Brunner;
D. Doyle;
B. Fransen;
A. Heras;
J. M. Lautier;
M. Linder;
L. Popken;
T. Nakagawa
Show Abstract
The paper provides a summary of the results of the assessment study conducted on the SPICA Telescope Assembly
(STA). SPICA (SPace Infrared telescope for Cosmology and Astrophysics) was selected for study as a mission of
opportunity within the science programme Cosmic Vision 2015-2025 of the European Space Agency, with a planned
launch in 2017. Observing in the 5 - 210 micron waveband, one of its major goals is the discovery of the origins of
planets and galaxies. ESA's main contribution is the provision of the SPICA Telescope Assembly (STA) featuring a 3.5
m primary mirror cooled to < 6K. A nationally funded European FIR instrument (SAFARI) would also be part of
SPICA's payload. Following an internal ESA study carried out in Q1 and Q2 2008, a parallel competitive industrial
study (phase A level) has been performed. The main results achieved during this study are summarised.
Large segmented UV-optical space telescope using a Hybrid Sensor Active Control (HSAC) architecture
Author(s):
Lee D. Feinberg;
Bruce Dean;
Tupper Hyde;
Bill Oegerle;
Matthew R. Bolcar;
J. Scott Smith
Show Abstract
Future large UV-optical space telescopes offer new and exciting windows of scientific parameter space. These
telescopes can be placed at L2 and borrow heavily from the James Webb Space Telescope (JWST) heritage. For
example, they can have similar deployment schemes, hexagonal mirrors, and use Wavefront Sensing and Control
(WFSC) technologies developed for JWST. However, a UV-optical telescope requires a 4x improvement in
wavefront quality over JWST to be diffraction-limited at 500 nm. Achieving this tolerance would be difficult using
a passive thermal architecture such as the one employed on JWST. To solve this problem, our team has developed a
novel Hybrid Sensor Active Control (HSAC) architecture that provides a cost effective approach to building a
segmented UV-optical space telescope. In this paper, we show the application of this architecture to the ST-2020
mission concept and summarize the technology development requirements.
Design for an 8-meter monolithic UV/OIR space telescope
Author(s):
H. Philip Stahl;
Marc Postman;
William R. Arnold Sr.;
Randall Hopkins;
Linda Hornsby;
Gary E. Mosier;
Bert A. Pasquale
Show Abstract
ATLAST-8 is an 8-meter monolithic UV/optical/NIR space observatory to be placed in orbit at Sun-Earth L2 by
NASA's planned Ares V cargo launch vehicle. ATLAST-8 will yield fundamental astronomical breakthroughs. A one
year mission concept study has developed a detailed point design for the optical telescope assembly and spacecraft. The
mission concept assumes two enabling technologies: NASA's planned Ares-V launch vehicle (scheduled for 2019) and
autonomous rendezvous and docking (AR&D). The unprecedented Ares-V payload and mass capacity enables the use
of a massive, monolithic, thin-meniscus primary mirror - similar to a VLT or Subaru. Furthermore, it enables simple
robust design rules to mitigate cost, schedule and performance risk. AR&D enables on-orbit servicing, extending
mission life and enhancing science return.
Stellar imager (SI): enhancements to the mission enabled by the constellation architecture (Ares I/Ares V)
Author(s):
Kenneth G. Carpenter;
Margarita Karovska;
Richard G Lyon;
D. Mozurkewich;
Carolus Schrijver
Show Abstract
Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) with over 200x the resolution of HST. It will
enable 0.1 milli-arcsec spectral imaging of stellar surfaces and the Universe in general and open an enormous new
"discovery space" for astrophysics with its combination of high angular resolution, dynamic imaging, and spectral
energy resolution. SI's goal is to study the role of magnetism in the Universe and revolutionize our understanding of: 1)
Solar/Stellar Magnetic Activity and their impact on Space Weather, Planetary Climates, and Life, 2) Magnetic and
Accretion Processes and their roles in the Origin & Evolution of Structure and in the Transport of Matter throughout the
Universe, 3) the close-in structure of Active Galactic Nuclei and their winds, and 4) Exo-Solar Planet Transits and Disks.
SI is a "Landmark/Discovery Mission" in 2005 Heliophysics Roadmap and a candidate UVOI in the 2006 Astrophysics
Strategic Plan and is targeted for launch in the mid-2020's. It is a NASA Vision Mission and has been recommended for
further study in a 2008 NRC report on missions potentially enabled/enhanced by an Ares V launch. In this paper, we
discuss the science goals and required capabilities of SI, the baseline architecture of the mission assuming launch on one
or more Delta rockets, and then the potential significant enhancements to the SI science and mission architecture that
would be made possible by a launch in the larger volume Ares V payload fairing, and by servicing options under
consideration in the Constellation program.
Lightweight optical barrel assembly structures for large deployable space telescopes
Author(s):
Peter A. Warren;
Mark J. Silver;
Benjamin J. Dobson
Show Abstract
Future space based telescopes will need apertures and focal lengths that exceed the dimensions of the launch vehicle
shroud. In addition to deploying the primary mirror and secondary mirror support structure, these large telescopes must
also deploy the stray light and thermal barriers needed to ensure proper telescope performance. The authors present a
deployable light and thermal optical barrel assembly approach for a very large telescope with a variable sun angle and
fast slew rate. The Strain Energy Deployable Optical Barrel Assembly (SEDOBA) uses elastic composite hinges to
power the deployment of a hierarchical truss structure that supports the thermal and stray light shroud material that form
the overall system. The paper describes the overall design approach, the key component technologies, and the design and
preliminary testing of a self deploying scale model prototype.
Optical modeling activities for NASA's James Webb Space Telescope (JWST): VI. secondary mirror figure compensation using primary mirror segment motions
Author(s):
Joseph M. Howard;
Lee D. Feinberg
Show Abstract
This is part six of a series describing the ongoing optical modeling activities for the James Webb Space
Telescope (JWST). The first two discussed modeling JWST on-orbit performance using wavefront
sensitivities to predict line of sight motion induced blur and stability during thermal transients. The third
investigates the aberrations resulting from alignment and figure errors after compensation of the controllable
degrees of freedom of the observatory (i.e. primary and secondary mirrors). This paper follows the theme of
the third, but considers the highly unlikely case where a gross figure error occurs on the secondary mirror.
We then compensate for this error using figure control on the primary mirror. The level of compensation as
well as the total motions required are evaluated and reported. Impact to image quality over the full field of
the observatory is also discussed.
Phase retrieval on broadband and under-sampled images for the JWST testbed telescope
Author(s):
J. Scott Smith;
David L. Aronstein;
Bruce H. Dean;
D. Scott Acton
Show Abstract
The James Webb Space Telescope (JWST) consists of an optical telescope element (OTE) that sends light to five
science instruments. The initial steps for commissioning the telescope are performed with the Near-Infrared Camera
(NIRCam) instrument, but low-order optical aberrations in the remaining science instruments must be determined
(using phase retrieval) in order to ensure good performance across the entire field of view. These remaining
instruments were designed to collect science data, and not to serve as wavefront sensors. Thus, the science cameras
are not ideal phase-retrieval imagers for several reasons: they record under-sampled data and have a limited range of
diversity defocus, and only one instrument has an internal, narrowband filter. To address these issues, we developed
the capability of sensing these aberrations using an extension of image-based iterative-transform phase retrieval
called Variable Sampling Mapping (VSM). The results show that VSM-based phase retrieval is capable of sensing
low-order aberrations to a few nm RMS from images that are consistent with the non-ideal conditions expected
during JWST multi-field commissioning. The algorithm is validated using data collected from the JWST Testbed
Telescope (TBT).
Non-invasive optical end-to-end test of a large TMA telescope (JWST) from the intermediate focus
Author(s):
Tony Whitman;
J. Scott Knight;
Mark Waldman;
Paul Lightsey
Show Abstract
The James Webb Space Telescope (JWST) requires testing of the full optical system in a cryogenic vacuum environment
before launch. Challenges with the telescope architecture and the test environment lead to placing removable optical test
sources at the Cassegrain intermediate focus of the Telescope. The Science Instrument suite will be used to align the
telescope and to verify the wavefront error. The Science Instruments capture test images that are analyzed using focus
diverse phase retrieval. The wavefront sensing algorithms have the large dynamic range required to measure the
relatively small wavefronts of interest in the presence of the large aberrations resulting from the off-axis source locations
at the intermediate focus. These inherent aberrations of the off-axis design are removed analytically from the measured
data. The test design and in-situ wavefront sensing process enables a number of tests to verify the alignment and optical
quality of the system.
Propellantless precision formation flying with photonic laser thrusters for large space telescopes
Author(s):
Young K. Bae
Show Abstract
One economically and technologically feasible bedrock structure for constructing large (diameter > 10 m) space
telescopes is a segmented or sparse aperture system with subcomponents in precision formation flight. For
UV/Visible/IR systems, initial targeting and targeting new objects to establish initial fringes requires the positioning
precision to nm - μm accuracy, thus the control system should be capable of the required precision positioning and
attitude controls without producing contaminations from thruster exhaust plumes. A nanometer accuracy contaminationfree
formation architecture, Photon Tether Formation Flight (PTFF), based on Photonic Laser Thrusters (PLTs) and
tethers has been proposed to exploit a force equilibrium formed by PLT thrust and tether tension for forming precision
persistent 3-D formation structures ideal for the large UV/Visible/IR space telescopes. The range of the PLT force can
theoretically extend over several kms. Under previous NASA sponsorship, we have successfully demonstrated a proofof-
concept PLT. In addition, the demonstrations of required laser components, optics and tracking technologies
developed under military laser applications now support that implementation of PLTs for large space telescopes is one
step closer to reality.
Optical pathlength stabilization between formation-flying air-bearing robots
Author(s):
Edward A. LeMaster
Show Abstract
The Precision Formation Control project seeks to demonstrate experimentally the capability to perform optical
pathlength stabilization of a visible-laser interferometer beam operating between two formation-flying robotic airbearing
space-vehicle emulators in a terrestrial laboratory environment, as a precursor to future separated-spacecraft
interferometer missions. The multi-tiered architecture utilizes laser sensors for inter-vehicle sensing, proportional
pneumatic thrusters for vehicular control, and a piezo-actuated delay line for optical pathlength control. In the lab
environment, relative stationkeeping between vehicles has been demonstrated to better than 9 μm in position and 11 μrad
in rotation (1-σ). Simultaneously, the inter-vehicle optical pathlength has been stabilized to less than 190 nm, 1-σ.
Working model of a gossamer membrane spectrographic space telescope
Author(s):
Thomas D. Ditto;
Joe Ritter;
John Valliant
Show Abstract
The nineteenth century Fraunhofer primary objective grating (POG) telescope has been redesigned with a secondary
spectrometer. The POG is embossed on a membrane and placed at an angle of grazing exodus relative to a conventional
spectrographic telescope. The result is a new type of telescope that disambiguates overlapping spectra and can capture
spectral flux from all objects over its free spectral range, nearly 40°. For space deployment, the ribbon-shaped membrane
can be stowed as a cylinder under a rocket fairing for launch and deployed in space from a cylindrical drum. Any length
up to kilometer scale could be contemplated.
The lunar radio array (LRA)
Author(s):
Joseph Lazio;
C. Carilli;
J. Hewitt;
S. Furlanetto;
Jack Burns
Show Abstract
The Lunar Radio Array (LRA) is a concept for a telescope sited on the farside of the Moon with a prime mission of
making precision cosmological measurements via observations of neutral hydrogen.
Vibroacoustic analysis and optimization of lightweight silicon carbide mirrors
Author(s):
Lucy E. Cohan;
David W. Miller
Show Abstract
Lightweight, actuated, silicon carbide mirrors are an enabling technology for large aperture, space-based optical
systems. These mirrors have the potential to improve optical resolution and sensitivity beyond what is currently
possible. However, launch survival is a key concern, especially for very lightweight mirrors. This work uses
an integrated modeling approach to determine the vibroacoustic response of mirrors subjected to launch loads
through the calculation of peak launch stresses in the silicon carbide substrate and in the actuators. The fully
parameterized model used with optimization and trade space exploration allows for the identification of key
design parameters for launch survival. The areal density, number or ribs, rib structure, and face sheet thickness
are identified as key variables that affect the launch stress and are varied in the optimization. Optimal designs, in
terms of lowest peak stress and lowest mass meeting launch stress requirements, are found, and iso-performance
is used to identify multiple sets of design parameters that meet launch survival requirements. This modeling
effort expands the knowledge of lightweight mirrors through the determination of technology limitations imposed
by the launch environment. The modeling method also allows for the addition of uncertainty analysis and launch
load alleviation techniques.
Minimizing high spatial frequency residual error in active space telescope mirrors
Author(s):
Thomas L. Gray;
Matthew W. Smith;
Lucy E. Cohan;
David W. Miller
Show Abstract
The trend in future space telescopes is towards larger apertures, which provide increased sensitivity and improved
angular resolution. Lightweight, segmented, rib-stiffened, actively controlled primary mirrors are an enabling
technology, permitting large aperture telescopes to meet the mass and volume restrictions imposed by launch
vehicles. Such mirrors, however, are limited in the extent to which their discrete surface-parallel electrostrictive
actuators can command global prescription changes. Inevitably some amount of high spatial frequency residual
error is added to the wavefront due to the discrete nature of the actuators. A parameterized finite element
mirror model is used to simulate this phenomenon and determine designs that mitigate high spatial frequency
residual errors in the mirror surface figure. Two predominant residual components are considered: dimpling
induced by embedded actuators and print-through induced by facesheet polishing. A gradient descent algorithm
is combined with the parameterized mirror model to allow rapid trade space navigation and optimization of the
mirror design, yielding advanced design heuristics formulated in terms of minimum machinable rib thickness.
These relationships produce mirrors that satisfy manufacturing constraints and minimize uncorrectable high
spatial frequency error.
Photonic muscle active optics for space telescopes (active optics with 10[sup]23[/sup] actuators)
Author(s):
Joe Ritter
Show Abstract
Presented is a novel optical system using Cis-Trans photoisomerization where nearly every molecule of a mirror
substrate is itself an optically powered actuator. Primary mirrors require sub-wavelength figure (shape) error in order to
achieve acceptable Strehl ratios. Traditional telescopy methods require rigid and therefore heavy mirrors and reaction
structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. Areal density can be
reduced by increasing actuation density. Making every molecule of a substrate an actuator approaches the limit of the
areal density vs actuation design trade space.
Cis-Trans photoisomerization, a reversible reorganization of molecular structure induced by light, causes a change in the
shape and volume of azobenzene based molecules. Induced strain in these "photonic muscles" can be over 40%. Forces
are pico-newtons/molecule. Although this molecular limit is not typically multiplied in aggregate materials we have
made, considering the large number of molecules in a mole, future optimized systems may approach this limit
In some π-π* mixed valence azo-polymer membranes we have made photoisomerization causes a highly controllable
change in macroscopic dimension with application of light. Using different wavelengths and polarizations provides the
capability to actively reversibly and remotely control membrane mirror shape and dynamics using low power lasers,
instead of bulky actuators and wires, thus allowing the substitution of optically induced control for rigidity and mass.
Areal densities of our photonic muscle mirrors are approximately 100 g/m2. This includes the substrate and actuators
(which are of course the same). These materials are thin and flexible (similar to saran wrap) so high packing ratios are
possible, suggesting the possibility of deployable JWST size mirrors weighing 6 kilograms, and the possibility of
ultralightweight space telescopes the size of a football field. Photons weigh nothing. Why must even small space
telescopes weigh tons? Perhaps they do not.
DMD multi-object spectroscopy in space: the EUCLID study
Author(s):
P. Spanò;
F. Zamkotsian;
R. Content;
R. Grange;
M. Robberto;
L. Valenziano;
F. M. Zerbi;
R. M. Sharples;
F. Bortoletto;
V. De Caprio;
L. Martin;
A. De Rosa;
P. Franzetti;
E. Diolaiti;
B. Garilli;
L. Guzzo;
P. Leutenegger;
M. Scodeggio;
R. Vink;
G. Zamorani;
A. Cimatti
Show Abstract
The benefits Astronomy could gain by performing multi-slit spectroscopy in a space mission is renown. Digital
Micromirror Devices (DMD), developed for consumer applications, represent a potentially powerful solution. They are
currently studied in the context of the EUCLID project. EUCLID is a mission dedicated to the study of Dark Energy
developed under the ESA Cosmic Vision programme. EUCLID is designed with 3 instruments on-board: a Visual
Imager, an Infrared Imager and an Infrared Multi-Object Spectrograph (ENIS). ENIS is focused on the study of Baryonic
Acoustic Oscillations as the main probe, based on low-resolution spectroscopic observations of a very large number of
high-z galaxies, covering a large fraction of the whole sky. To cope with these challenging requirements, a highmultiplexing
spectrograph, coupled with a relatively small telescope (1.2m diameter) has been designed. Although the
current baseline is to perform slit-less spectroscopy, an important option to increase multiplexing rates is to use DMDs as
electronic reconfigurable slit masks. A Texas Instrument 2048x1080 Cinema DMD has been selected, and space
validation studies started, as a joint ESA-ENIS Consortium effort. Around DMD, a number of suited optical systems has
been developed to project sky sources onto the DMD surface and then, to disperse light onto IR arrays. A detailed study
started, both at system and subsystem level, to validate the initial proposal. Here, main results are shown, making clear
that the use of DMD devices has great potential in Astronomical Instrumentation.
Low dispersion ghost-controlled optical window/combiner component
Author(s):
Paul Atcheson
Show Abstract
A key consideration in designing optical systems, instruments, or test setups requiring windows or beam combiners is
the potential for ghost images to be produced from reflections off the window/combiner surfaces. These ghost images
will affect the optical system performance and the level to which that performance can be demonstrated during
verification testing. Two common solutions for this are to use anti-reflection coatings and to use wedged substrates.
Each has performance implications when used in spectrally broadband systems. The use of coatings alone on
windows/combiners results in modest reduction (<100X) of ghost image intensity that can be inadequate when using or
testing systems designed to find weak targets near bright objects. Using wedged substrates to shift ghost images outside
an image region of interest will introduce chromatic aberrations that limit the fundamental broadband system imaging
performance. In this paper we present design parameters for window/combiner assemblies that shift ghost images from
a region of interest while controlling the chromatic aberrations to a level whereby the system imaging performance is not
adversely affected even for broadband imaging systems with high angular resolution. We then present an example
demonstrating the performance of a typical low dispersion, ghost-controlled window/combiner assembly.
Measurement of vibration environment of 6m-diameter radiometer thermal vacuum chamber in JAXA
Author(s):
Haruyoshi Katayama;
Yasuji Yamamoto;
Masashi Miyamoto;
Hideki Saruwatari;
Hidehiro Kaneda;
Yoshio Tange
Show Abstract
Space-borne large optics will be required in future missions for astronomy and earth observations. In order to realize
large-optics missions, JAXA has started the study of the ground measurement techniques of large optics. The 6m
diameter radiometer thermal vacuum chamber (6m chamber) at Tsukuba Space Center will be used for tests of JAXA's
future large-optics missions like Space Infrared Telescope for Cosmology and Astrophysics (SPICA). We measured the
vibration environment of the 6m chamber for the feasibility study of precise optical measurement. We placed a test
mirror inside the chamber and measured the surface figures of the mirror from outside the chamber with a high-speed
interferometer, while the chamber was being vacuum-pumped and cooled by liquid nitrogen; we also directly measured
the vibrational levels with accelerometers concurrently. The measurements were performed for each phase of the
chamber system operation including pumping and cooling processes. This paper presents the results about optical
measurement under the vibration environment on the 6m chamber. We confirm that the vibrations from pumps and
shroud have negligible effects on optical measurements owing to a vibration isolation system in the 6m chamber.
Optical testing of the Kepler Photometer in a thermal vacuum environment at Ball Aerospace
Author(s):
Mark A. Martella;
Don A. Byrd;
Stew Willis;
Peter Spuhler;
Noah Siegel;
Chris Stewart
Show Abstract
The Kepler spacecraft and telescope were designed, built and tested at Ball Aerospace & Technologies Corporation in
Boulder, Colorado. The Kepler spacecraft was successfully launched from NASA's Kennedy Space Center on March 6,
2009. In order to adequately support the Kepler mission, Ball Aerospace upgraded its optical testing capabilities. This
upgrade facilitated the development of a meter-class optical testing capability in a thermal vacuum (TVAC)
environment. This testing facility, known as the Vertical Collimator Assembly (VCA), was used to test the Kepler
telescope in 2008. Ball Aerospace designed and built the VCA as a 1.5m, f/4.5 collimator that is an un-obscured system,
incorporating an off-axis parabola (OAP) and test flat coated for operations in the VIS-IR wavelength region. The VCA
is operated in a large thermal vacuum chamber and has an operational testing range of 80 to 300K (-315 to 80°F). For
Kepler testing, the VCA produced a 112nm rms wavefront at cryogenic temperatures. Its integral autocollimation and
alignment capabilities allowed knowledge of the collimated wavefront characteristics to <5nm rms during final thermal
vacuum testing. Upcoming modifications to the VCA optics will bring the VCA wavefront to <20nm rms. The VCA
optics are designed and mounted to allow for use in either a vertical or horizontal orientation without degradation of the
collimated optical wavefront.
Semiconductor laser tracking frequency distance gauge
Author(s):
James D. Phillips;
Robert D. Reasenberg
Show Abstract
Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will
require a spaceworthy laser distance gauge of substantially improved performance. The Tracking Frequency Gauge
(TFG) uses a single beam, locking a laser to the measurement interferometer. We have demonstrated this technique with
pm (10-12 m) performance. We report on the version we are now developing based on space-qualifiable, fiber-coupled
distributed-feedback semiconductor lasers..